LIBS Analysis of Optical Surfaces and Thin Films

Abstract

Elemental analyses of thin films and optical surfaces with complex compositions are challenging as the standard analytical techniques based on measurement calibration are difficult to apply. In this chapter, we show that calibration-free laser-induced breakdown spectroscopy presents a powerful solution, enabling rapid quantitative analyses of multi-elemental thin films or tiny surface volumes of optical materials with high analytical performances. Examples are given for classically polished optical glass and a nickel-chromium-molybdenum alloy film of 150 nm thickness. Thus, broadband spectra, recorded under experimental conditions that enable simple and accurate modeling of plasma emission, are processed via a calibration-free approach based on the calculation of the spectral radiance of a plasma in local thermodynamic equilibrium to deduce the elemental composition. The validation via energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, and Rutherford backscattering spectrometry illustrates that calibration-free LIBS is not only a promising tool, but already a reliable analytical technique.